Electron tube



Jan. 11, 1927. 1,613,948

R. V. L. HARTLEY ELECTRON TUBE Filed Sept. 2, 1924 2/ D l, f /6 /7 292 In Ajgeiv/f Z3 2 u u u 2 24 X .l 24 /4 27 Patented Jan. 11, 1927.

2 v 1,513,948 PATENT "OFFICE.

RALPH V. I4. HARTLEY, OF SOUTH ORANGE, NEW JERSEY, ASSIGNOB IO wns'rm,

ELECTRIC COMPANY, INQOBPOBATED, OFNEW YORK, 11'. Y,, LOOBIOB-LTIOI OI n'zaw YORK.

ELEOTRON TUBE.

. Application and September 2, 1924. I Sci-111110. asses.- 1

This invention relates to wave transmission, and more particularlyto the conversion of mechanical waves mto electrical waves.

Objects of the invention are to efliciently p are attained in a space current device having a mechanical frequency selecting system arranged to selectively transmit mechanical waves through a flexible portion of the wall of the device, the mechanical waves causing 90 the size of the apertures in the grid or space current control element of the device to vary, thereby to produce space current waves corresponding to the mechanical waves. The

mechanical waves may be induced by speech orother sound waves impinging on an acoustic diaphragm coupled with the filter.

In the accompanying drawing, Fig. 1 is a diagrammatic view, partly in section, of a I space current device constructed in accord- 30 ance with the invention, Fig. 2 is a fragmental view of a modification of Fig. 1 between dotted" lines X and Y, and Fig. ,3 .is a plan of one of the grids in Fig. 2.

Referring to Fig. 1, the evacuated sealed chamber 10, having walls of glass, or other suitable insulating material, is provided with two oppositely disposed axially aligned tubes 11 and 12 which may be of metal, or other suitable material, sealed to the glass 10. Tube 11- is sealed at its outer end by the flexible diaphragm 13, tube 12 being similarly sealed at its outer end by flexible diaphragm 14. Chamber 10 encloses a filamentary cathode 15, the coaxial cylindrical anode 16, and helical spring grid 17 interposedcoaxially between cathode 15 and anode 16. Cathode 15 is heated by a source ofcurrent 18 to cause the emission of electrons or space current. The source of space current 19 is connected in the usual manner between cathode l5 and anode 16, the space current passingthrough the primary winding of output transformer 20, which provides an output circuit for the 'chanical resistance 27 of any nating impedance requisite for a uniform response over the frequency range of transmis- A mechanical frequency selecting system or wave transmission filter 21, supported in tube 11, is made up of a plurality of masses-v 22' supported in spaced relation from each other within tube 11 and coupled together in 1 series with each other and with diaphragm 13' by means of the elastic elements or springs 23. Each of the masses 22 is, or may be, concentrated and supported-near the center of a separate diaphragm or other suitable "supporting element 24, mounted in tube 11. Diaphragms 24 are spaced apart in substantially parallel relation, and may entirely, or only partially, close the opening through tube 11. Preferably, supports 24 have very small or negligible stiffness, while springs 23 preferably have very small or negligible masses. The left hand end of grid 17 is attached, preferably by means of electrical insulation 17 to mass 22 at the ri ht hand terminal of filter 21, while the rig t hand end of grid 17 is similaply attached to mass 22 at the left hand terminal of. filter 25.

Filter 25 is'of similar construction to filter 21 and is supported in tube 12 in a man.- ner similarto that described in connection with filter 21 and tube 11. The masses of diaphragms 13 and 14 function similarly to the concentrated masses 22. Diaphragm 14 is coupled by means of spring 26 to the me- I well known form, being illustrated as a p unger 28 subjected to the viscous or frictional action of the comminuted material 29 in container 30.

Filters 21 and 25 may be treated analytically similarly to electric wave filters. Masses" l tby virtue of their stiffness correspond to capacity elements connected in series with the inductances corresponding to these diaphragms. Springs 23, 17 and 26 correspond to shunt capacity elements. Mechanical 1 6-.

sistance 27 provides a simple form of termi-' sion of the filter. When the space current device is to be employed as a telephone transmitter, diaphragm 13 may be employed as an acoustical diaphragm.

For the purpose of-transmitting, without substantial distortion, speech or other sound waves within a useful frequencyrange, filters 21 and 25 may be designed to efiiciently transmit, without serious attenuation, al waves having frequencies lying within a range having predetermined limits, while waves of all frequencies lying outside this range are greatly attenuated or substantially extinguished. The design of such a filter may be readily accomplished by reference to well known data employed in the computation .of the constants of electric wave filters, use being made of the relation, explained above, between the constants of an electric filter and of a mechanical filter. A typical form of electrical filter, corresponding to mechanical filters 21 and 25, is shown in Fig. 7 of G. A. Campbell Patent 1,127,113, dated May 22, 1917, and the method of designing such a filter is explained in the patent.

In order to withstand the pressure of the atmosphere, diaphragms 13 and 14 are comparatively stiff. The amplitude of the motion of these diaphragms is, therefore, small, and the motion of grid 17 is, accordingly small. In order to increase the deflection of grid 17, filters 21 and 25 may be tapered, that is, the constants of successive sections of the filters may converge in value. It has been found that by select ag proper values for such a tapered filter a suitable deflection may be produced in grid 17. The filter may have any number of recurrent sections 22, 23 required to produce the desired transmission characteristic.

In a specific example, a seven-section filter capable of transmitting without distortion wave frequencies lying between 200 cycles and 2500 cycles per second contains elements having the constants given below, the values in the first column representing the masses in successive sections of the filter 21 start ing with diaphragm 13 and going to the right, while the values given in the other column represent the reciprocals of the clasticities of springs 23. Diaphragms 13 and 14 each have a mechanical resistance of 1000 dynes, the mechanical resistance being a measure of the force required to impart a.

velocity of one centimeter per'second to the diaphragm. The mass 22 in each filter 21 and 25, nearest to grid 17, has a mechanical resistance of 100 dynes.

Dyp es per can me er i deflection. gm Multlply by 10.

In this instance, diaphragms 13 and 14 each have a mass of such value that it may be considered concentrated at the center of the diaphragm as a mass of .664 grams, the filters 21 and 22 being made up of sections which contain successively smaller masses 22 as they approach grid 17.

In the operation of the space current device sound waves lying between the frequency limits of transmission of filter 21 are transmitted from diaphragm 13 through filter 21, grid 17 and filter 25 to resistance 27, this resistance preventing reflection of the transmitted wave back through the filter. Owing to the relative movements of opposite ends of the elastic helical grid 17, the aperin size and produce corresponding fluctuations in the space current through the device,

the resulting wave being transmitted to output transformer 20. The electric wave thus produced corresponds closely to the mechani cal or acoustic wave impressed upon dia phragm 13, and the amplitude of the electrical wave is enhanced by the amplifying action of the three element space current device.

Instead of sealing tubes 11 and 12 by diaphragms 13 and 14 at the outermost ends of the tubes, any one of the supports 24 may be employed as a sealing diaphragm, and if this is done, it is preferable to arrange atapered filter on each sideof the sealing diaphragm in order to avoid a sharpdiscontinuity in the transmission characteristic of the filter at this diaphragm.

In Fig. 2, chamber 10 contains the cathode 15, the anode 31 and the two grid elements 32 and 33 interposed between the cathode and anode. Grid 32 is rigidly coupled to mass 22 of filter 21, preferably by electricalinsulation. Grid 33 is elastically coupled at one end to grid 32 by means of spring 34, and rigidly coupled at its other end to mass 22 of filter 25, grid 33 being preferably insulated from filter 25. Each of the grids 32 and 33 is provided with the parallel apertures 36 as shown in Fig. 3, which are disposed transversely to the direction of move ment of the grids, the movement being produced by deflection of diaphragms 24 and spring 34. The apertures 36 in the two grids register with each other in such a manner that motion of grid 32 with respect to grid 33 varies the efiective size of the efiective apertures through the grid as a whole between cathode 15 and anode 21. Grids 32 and 33 are held parallel to each other by the stiffness and configuration of their supports.

When grid 32 vibrates longitudinally, that is, from left to right and vice versa, in the figure, in response to mechanlcal waves from filter 21, grid 33 moves relatively thereto and m a parallel direction in accordance with the wave motion transmitted thereto,

tures between adjacent turns of the grid vary .thus producing shiftsbetween grids 32 and 33 and corresponding variations in the effective size 0 pedance of the space current device roduce electrical waves corresponding to t e mechanical waves.

It will be' noted that grid 17, Fig. 1, and

grid 31, 32, Fig. 2, are so coupled to filters a other through the elastic coupling between the sides of the aperture the deflection of this coupling produces corresponding variation in the size of the aperture and similar variations in the impedance of or the space current throu h the device.

While the invention has been described with specific reference to certain species illustrative of the invention, it is to be understood that the invention may be carried out in various ways and be embodied in. various forms as defined in the appended claims.

What is claimed is:

1. In a space current device, a movable space current control element, and a'tapered mechanical wave transmission filter coupled therewith. I

2. In, a space .current device, a movable space current control element, a vibratory 1 diaphragm, and a tapered wave filter connected between said diaphragm and said control element. 1

3. In a space discharge device, a space discharge path, a control electrode adapted to vary the discharge by its motion, an enclosing vessel, and means for transmitting wave motion to said electrode, said means 1 element having at least a portion which is comprising a tapered wave filter having its stiff end connected to the wall of said vessel and its flexible end connected to said electrode. v v

4. In a space discharge device, a discharge path, a control electrode, an enclosing vessel,

and a mechanical coupling system connected to said electrode and to the wall of said vessel, said coupling system comprising a broad band wave filter adapted to transform the wave motion, whereby a small motion impressed upon the wall of ,the enclosing vessel is converted to a proportionately increased motion of said electrode.

5. In a space discharge device, a discharge transfer motion from t e walls of said vessel to said electrode, said coupling stem comprising a doubly tapered filter aving end the apertures presented by them. The resulting variations in the imsections of high impedance and middle sections of low impedance, saidend sections being connected to portions of the walls of sa1d vessel and sald control electrode being connected to a point in a middle section.

6. In a space current device, a longitudinally extensible grid havin transverse aperturestherein, and a mechanical frequen-' ble portion, a mova le element within said vessel, and a mechanical frequency selecting system connected to said movable element and to said flexible portion, said system having recurrent sections.

9. In combination, a vessel having a pluf rality of flexible portions, an element within said vessel having relatively movable parts, and a plurality of mechanical frequency selecting systems, each of said flexible portions being connected by a single one of said frequency selecting systems to a separate one of said movable parts.

10. In a space current device, a grid ,hav-j ing an aperture, the opposite sides of which are elastically coupled together, a mechanical frequency selecting system coupled to one side of said aperture, and another mechanical frequency selecting system coupled to the other side of said aperture.

11. In a space current device, a control element having at least a portion which is movable, and a-mechanical frequency selecting system coupled to said movable portion, said system including a lurality of springs of predetermined elasticity, and a plurality of predetermined masses coupled together in series by said springs. q

12. In a space current device, a control movable, and a mechanical frequency selectsaid system including-a plurality of springs of predetermined elasticity, a plurality of predetermined masses coupled together by said springs, and means for supporting said masses in position.

13. In a space current device, a control element. having at least a portion which is movable, a mechanical frequency selectin system coupled to said movable ortion, sai system including a plurality o? springs of predetermined elasticity a plurality of predetermined masses 'coupledtogether by said springs, and a separate diaphragm supporting each of said masses.

' 14. Ina space current device, a control element having two portions which are movable with respect to each other, and a sep ing system coupled to said movable portion,

arate mechanical frequency selecting system cou led to each of said portions, each of sai systems having recurrent sections.

15. In a space current device, a control element having at least a. portion which is movable, a mechanical frequency selecting system coupled to said movable portion,

a mechanical resistance coupled to one. of said sections. I

16. In a telephone transmitter, aspace current device having an aiiode,a cathode and a control element, means whereby a space current is produced between said anode and portion which is movable, a tu'beextending from one side of said vessel, and amechanical frequency selectmg system housed 1n said tube and coupled to the movable portion 0i said control element. 1-

- 18. In a space current device, a'vessel containing a control element having two portions movable with respect :toeach other, a pair of tubes separately extending from said vessel, and a separate mechanical frequency selecting system housed in each said tube and coupled respectively to the movable portions of said control element.

19. In a space current device, a vessel con- 1 taining a control element having two por- .control element. said system having. recurrent sections, and

tions movable. with respect to each other, a pair of axially aligned tubes extending respectively from opposite sides of said vessel, and amechanical frequency selecting s stem housed in each said tube and coup ed respectively to the movable portions of said '20. 'In wave transmission apparatus, a vessel containing an element having at least a portion which is=movable, and a mechanical frequency selecting system coupled to the movable portionof said element, said system including a diaphragm forming a. portlon of the wall of said vessel.

. -21. In Wave transmission apparatus, a vessel containing an element having at least a portion which is movable, and a mechanical frequency selecting system coupled to the movable portion of said element, said system including a plurality of spaced diaphragms supported by said vessel, one of said diaphragms forming a portion of the wall of said vessel, eachof'said other diaphragms having a mass concentrated near its center, and elastic couplings between said masses.

22. In a space current device, a grid hav- "ing an aperture the o posite sides of which are elastically couple together, a mechanical frequency selective'system coupled to one side of said aperture, another mechanical frequency selecting system coupled to the other side of said aperture, and a mechanical rsistance coupled to said other mechanical frequencysystem.

In witness whereof, I hereunto subscribe my'name this 26th-day of August, A. D. 1924.

RALPH V. L. HARTLEY. 

